I don't know what 315 degrees has to do with anything.
Each motor has a firing event every 90 degrees of crankshaft rotation. 720 crankshaft degrees of rotation makes one complete cycle on each motor. My best thinking tells me that the rear motor should be connected to the front motor with the rear motor staggered 45 degrees from the front one. Front motor at zero, rear motor at either 45 ATDC or 45 BTDC. That way, you get a firing event every 45 degrees instead of every 90 like with one motor only.
I would also use a large rubber biscuit to mate them instead of tieing them together solid with hubs and chain. I've seen these before, but I can't remember where. Maybe a marine piece.